The present disclosure relates generally to interleukin-10 (IL-10) peptides and to isolated antibodies that specifically bind to the IL-10 peptides. The present disclosure further relates to animal feed additives comprising the IL-10 peptides and/or the isolated antibodies. The present disclosure further relates to methods for treating gastrointestinal protozoan infection, and in particular, maintaining growth in an animal infected with a protozoan infection by administering the IL-10 peptides and the isolated antibodies that specifically bind to the IL-10 peptides.
Coccidiosis is a common parasitic protozoan infection of livestock and poultry species, and is capable of infecting both invertebrates and vertebrates, including humans. Coccidiosis in chickens is caused by infection of the epithelial cells lining the alimentary tract and the cells of associated glands by the parasitic protozoa of the genus Eimeria. The Eimeria genus includes at least seventeen species capable of infecting birds, most notably E. tenella, E. necatrix, E. maxima, E. brunette, and E. acervulina. 
The life cycle of Eimeria takes about four to seven days to complete and begins when active oocysts are ingested by a host. The parasite obtains nutrients from the host and is prolific in nature, although the parasite will generally stop multiplying before causing the death of the host. Coccidiosis disrupts the digestive tract and enteric flora of an animal. Symptoms of the disease include weight loss, growth suppression, diarrhea, bloody diarrhea, anorexia, necrotizing enterocolitis, and sometimes death. Coccidiosis in poultry alone has a severe economical effect. Specifically it is estimated to cost the poultry industry one billion dollars a year in reduced animal performance.
Coccidiosis has generally been treated using anti-Coccidial drugs in animal feed and administering vaccinations using an attenuated Coccidiosis vaccine. Due to the potentially adverse effects on humans and animals, the use of anti-Coccidial drugs and antibiotics is being phased out in many countries including European countries and Japan. In addition, the increased emergence of drug resistant strains and the increased costs of developing new drugs have led to an interest in developing alternative methods for controlling Coccidiosis. Using vaccines for treating Coccidiosis, for example, has many disadvantages, including risk that the vaccine will not generate a sufficient amount of antibodies for treating the infection. Additionally, vaccination requires several weeks to produce antibodies, leaving a several week period in which the immunized birds may become infected with Coccidiosis. Attenuated vaccines may also negatively impact animal growth, resulting in suppression of animal performance.
In light of the current problems associated with controlling Coccidiosis using drugs and/or vaccines, there exists a need for a feed additive capable of treating Coccidiosis and other gastrointestinal protozoan infections, while maintaining growth in an animal. Additionally, there exists a need for a natural feed additive, acceptable by regulatory authorities throughout the world, and which comports with global trends aimed at eliminating drugs and antibiotics from animal feed and the resulting animal products.